This laboratory has worked in CSF physiology and especially on arginine vasopressin (AVP) in CSF. We have studied the effects of subarachnoid hemorrhage on CSF formation and absorption, and upon the ventricular system morphologically; we have also assessed the changes in vasopressin in blood and CSF that accompany experimental subarachnoid hemorrhage and evaluated the effects of vasopressin infusion into the ventricular system of normal dogs and rabbits. We have found that intracerebroventricular infusion of vasopressin increases CSF absorption. Over the next year the laboratory will specifically test the hypothesis that vasopressin increases CSF absorption by increasing pinocytotic activity at CSF absorptive sites. Ventriculo-cisternal perfusion at high and normal CSF pressure and at high and low vasopressin concentrations will be accompanied by an analysis of vasopressin levels and pinocytotic activity. Vasopressin antagonists will be used to attempt to block this effect and agonists to produce it selectively. If time and funds allow, we will also assess the distribution of AVP in the CSF of unanesthetized sheep after ventricular perfusion. These studies will allow intensive investigation of one important potential role of vasopressin in CSF and provide valuable information about the distribution of this peptide within the CSF compartment.